- Wearing two face masks can almost double one's protection against SARS-CoV-2 particles
- Researchers tested the efficacy of surgical and cloth masks
- How well the mask fits is also extremely important to ensure that Covid-19particles are filtered
New research has established that wearing two face masks can almost double the effectiveness of filtering out SARS-CoV-2 particles, preventing them from reaching the nose and mouth, and potentially causing Covid-19.
The study published in JAMA Internal Medicine compared the fitted filtration efficiency (FFE) of commonly available masks – worn single, double, or in other combinations.
Measuring the efficiency of masks
The researchers assessed one female volunteer and two male volunteers to investigate the effectiveness of face coverings. They filled a 10-foot by 10-foot (3m by 3m) stainless-steel exposure chamber with small salt-particle aerosols and tested combinations of masks to measure how effective they were at keeping particles out of the participants' breathing space.
The volunteers wore double surgical and cloth masks, and then a combination of the two masks. They also tested single cloth masks and single surgical masks.
Double and well-fitted is better
The study findings show that wearing a medical procedure mask underneath a cloth mask provided the best improvement to FFE of all the combinations evaluated. A surgical mask without alterations to the fit is about 40–60% effective at keeping Covid-19-sized particles out, while a cloth mask is about 40% effective.
The FFE of procedure masks when doubled, or when worn underneath reusable cloth face coverings is consistent with minimising leaks between the mask and facial skin, including the bridge of the nose.
When researchers enhanced the seal between the mask and the facial skin, the FFE significantly improved. This demonstrates that the fit and not the material is the most important factor in mask-wearing.
"We've found that wearing two loosely fitted masks will not give you the filtration benefit that one snug-fitting procedure mask will. And with the current data supporting how effective mask-wearing is at preventing the spread of Covid-19, the best kind of double-masking is when you and the person you are interacting with are each correctly wearing a very snug-fitting mask," says lead study author Dr Emily Sickbert-Bennett in a press statement.